In recent years, in addition to low cost and high speed, high reliability and high quality have been required for a wide area network, such as a metro Ethernet (registered trademark). Accordingly, fault recovery and redundancy, such as those provided by SONET (synchronous optical network)/SDH (synchronous digital hierarchy), have been required.
In existing networks, as shown in FIG. 11, a plurality of flows (paths) are provided in each of links in a network. Fault is monitored on a flow-to-flow basis. If an error occurs, a Work path system is switched to a Protection path system. In general, in existing networks as shown in FIG. 11, a plurality of links are provided between apparatuses, and several hundred flows are provided in each of the links.
In such existing networks, fault monitoring is accomplished by individual apparatuses. If a fault is detected, a maintenance packet (fault information) is sent to an upstream interface (IF) unit in the apparatus, and the upstream IF unit examines the maintenance packet. Thus, the system can be switched.
For example, this fault monitoring is described with reference to FIG. 12. In FIG. 12, an apparatus A is connected with an apparatus B using a Work path via an IF unit (#6) and a Protection path via an IF unit (#7). In this case, each of the IF unit (#6) and the IF unit (#7), which are disposed on an ingress side of the apparatus A, identifies whether, for example, a received packet input to the unit itself is a maintenance packet, such as CC of Service-OAM, or a normal data packet (refer to FIG. 13). In addition, each of the IF unit (#6) and the IF unit (#7) acquires information indicating whether the packet is destined for a central processing unit (CPU) or not and a number assigned to each of the flows (a flow ID). Note that the term “CC of Service-OAM” refers to continuity check of service-operations administration maintenance.
If each of the IF unit (#6) and the IF unit (#7) identifies that the input packet is a maintenance packet, flow identification and destination control indicated by (1) shown in FIG. 13 are performed. More specifically, each of the IF unit (#6) and the IF unit (#7) sends, to the CPU of the IF unit itself, the maintenance packet with a flow ID attached thereto. Subsequently, the CPU of the IF unit (#6) or the IF unit (#7) sends the maintenance packet to an IF unit (#1), which is one of upstream units identified by the flow ID, via a Main CPU Unit (MCU) unit connected thereto using a control bus. Upon detecting the occurrence of a fault in the Work path through the received maintenance packet, the IF unit (#1) switches the Work path to a Protection path and performs data control.
However, if each of the IF unit (#6) and the IF unit (#7) identifies that the input packet is a data packet, flow identification and destination control indicated by (2) shown in FIG. 13 are performed. More specifically, each of the IF unit (#6) and the IF unit (#7), which are units disposed on an ingress side, sends the data packet to the IF unit (#1), which is one of upstream units identified by the flow ID, via a data bus. In this way, in existing processing, a maintenance packet is sent to an upstream target IF unit over the low-speed control bus by unicasting.
When a plurality of upstream IF units are provided, that is, when a plurality of upstream IF units use a single Work path and a single IF unit, the path switching process can be performed in a similar manner. For example, as shown in FIG. 14, the IF unit (#6) disposed on the ingress side sends a received maintenance packet to the MCU unit. The MCU unit then detects the destinations of the received maintenance packet from, for example, the header of the packet and generates copies of the maintenance packet for the number of destinations. Thereafter, the MCU unit sends the generated maintenance packets to IF units (#1, #2, and #4) which are detected destinations of the packet and are units disposed on an egress side. Subsequently, upon detecting the occurrence of a fault in the Work path through the received maintenance packet, each of the IF units (#1, #2, and #4) switches the Work path to a Protection path and performs data control.
In an existing network as described in Japanese Unexamined Patent Application Publication No. 2008-211704, path protection in which the Work path is switched to the Protection path is performed. Note that, in general, a control system bus having a transfer rate of several hundred Mbps is used for the path through which the maintenance packet illustrated in FIGS. 12 and 14 is sent to the IF unit (the upstream IF unit) disposed on the egress side, that is, the path from the unit on the ingress side to the unit on the egress side via the MCU unit. In addition, processing units in each of the IF units are connected with one another using a control system bus having a transfer rate of several hundred Mbps.